The reason is that con, prn, lpt1..lpt9, etc are underlying devices from the time dos was written. so if u r allowed to create such folders, there will be an ambiguity in where to write data when the data is supposed to go to the specified devices. In other words, if i want to print something, internally what windows does is -- it will write the data to the folder prn (virtually u can call it a folder, i mean prn, con, etc are virtual folders in device level). So if we are able to create con folder, windows will get confused where to write the data, to virtual con folder or real one.